Background: Researchers suggest benefits for cooperative learning, but often fail to control for choosing to engage cooperatively, ACT scores or early course performance. Objective: To observe the effects of choosing cooperative work on exam performance in an Introduction to Psychology Course, while controlling for early exam performance and ACT. Method: Data from 261 students assessed the interaction between choice to work cooperatively, alone or being required to work alone while controlling for ACT Score and performance on early tests, respectively. Results: We observed an interaction between Group and ACT on final exam scores, indicating students who worked cooperatively showed the greatest exam benefits at lower ACT scores. Additionally, a trend toward a significant interaction was found between group and early exam performance, indicating a possible benefit for choosing to work cooperatively for low performers. Conclusion: Choosing to engage in cooperative learning may decrease ACT-indicated skill differences and early exam success on final exam performance. Teaching Implications: To decrease the impact of ACT-influenced effects on exam scores, choice to complete cooperative learning activities should be offered in Introduction to Psychology courses.